This invention relates to a bobbin case for a sewing machine having a horizontal axis rotating hook and, more particularly to the support thereof.
In a sewing machine having a horizontal axis rotating hook there is traditionally provided an open cavity formed in the free end of the hook, the cavity having an annular raceway formed therein. The bobbin case has a structure that closely mates with this raceway thereby providing bearing support so that the weight of the bobbin case is supported by the rotating raceway while the bobbin case is restrained from rotation. Inherent in this type of construction is the necessity to manufacture the parts to very close tolerance, thus, increasing their costs. Additionally, the raceway must be lubricated in order to achieve a reasonable operating life. Another disadvantage of this construction is that lint frequently accumulates in the confined area between the bobbin case and the cavity walls of the hook, requiring frequent cleaning. One method to alleviate some of these problems is disclosed in U.S. Pat. No. 239,998, Apr. 12, 1881, Willcox et al, which describes a hanging bobbin case that is suspended from a stationary support finger. There is sufficient clearance between the bobbin case and the internal walls of the hook to permit passage of a loop of thread. This clearance, however, is minimized so that the walls of the hook will limit sideways movement of the bobbin case. Thus, in operation the bobbin case, due to a variety of causes such as forces exerted through the thread by the beak and the take up lever and vibrations normally occurring in the sewing machine, will swing from side to side and thereby contact the internal walls of the rotating hook. This can intermittently inhibit passage of the loop of thread thereby adversely affecting stitch formation particularly when such interference with passage of the thread occurs while the needle thread loop is being expanded and drawn about the bobbin case by the loop taker. The present invention overcomes these difficulties of the prior art by the use of novel but relatively simple structure.